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Chapter 2: The Research
Enterprise in Psychology
The Scientific Approach:
A Search for Laws
 Basic assumption: events are governed by
some lawful order
 Goals:
1. Measurement and description
2. Understanding and prediction
3. Application and control
Figure 2.2 Flowchart of
steps in a scientific
The Scientific Method: Terminology
 Operational definitions are used to clarify
precisely what is meant by each variable
 Participants or subjects are the organisms
whose behavior is systematically observed in
a study
 Data collection techniques allow for
empirical observation and measurement
 Statistics are used to analyze data and
decide whether hypotheses were supported
Table 2.1 Key Data Collection Techniques in Psychology
The Scientific Method: Terminology
 Findings are shared through reports at
scientific meetings and in scientific
journals – periodicals that publish technical
and scholarly material
 Advantages of the scientific method: Clarity
of communication and relative intolerance
of error
 Research methods: General strategies for
conducting scientific studies
Peer Review of Scientific Articles
 The process of publishing scientific studies
allows other experts to evaluate and critique
new research findings.
 They carefully evaluate each study’s methods,
statistical analyses, and conclusions, as well
as its contribution to knowledge and theory.
 The purpose of the peer review process is to
ensure that journals publish reliable findings
based on high-quality research.
Experimental Research: Looking for Causes
 Experiment = manipulation of one variable
under controlled conditions so that resulting
changes in another variable can be observed
 Detection of cause-and-effect relationships
 Independent variable (IV) = variable
 Dependent variable (DV) = variable affected
by manipulation
 How does X affect Y?
 X = Independent Variable, and Y =
Dependent Variable
Experimental and Control Groups:
The Logic of the Scientific Method
 Experimental group
 Control group
 Random assignment
 Manipulate independent variable for one
group only
 Resulting differences in the two groups
must be due to the independent variable
 Extraneous and confounding variables
Figure 2.6 The basic elements of an experiment
Advantages and Disadvantages
of Experimental Research
 Strengths:
 conclusions about cause-and-effect can be
 Weaknesses:
 artificial nature of experiments
 ethical and practical issues
Descriptive/Correlational Methods:
Looking for Relationships
 Methods used when a researcher cannot
manipulate the variables under study
 Naturalistic observation
 Case studies
 Surveys
 Allow researchers to describe patterns of
behavior and discover links or associations
between variables but cannot imply causation
Statistics and Research:
Drawing Conclusions
 Statistics – using mathematics to organize,
summarize, and interpret numerical data
 Descriptive statistics: organizing and
summarizing data
 Inferential statistics: interpreting data and
drawing conclusions
Descriptive Statistics:
Measures of Central Tendency
 Measures of central tendency = typical or
average score in a distribution
 Mean: arithmetic average of scores
 Median: score falling in the exact center
 Mode: most frequently occurring score
 Which most accurately depicts the typical?
Figure 2.11 Measures of central tendency
Descriptive Statistics: Correlation
 When two variables are related to each other,
they are correlated.
 Correlation = numerical index of degree of
 Correlation expressed as a number
between 0 and 1
 Can be positive or negative
 Numbers closer to 1 (+ or -) indicate
stronger relationship
Figure 2.13 Positive and negative correlation
Figure 2.14 Interpreting correlation coefficients
Prediction, Not Causation
 Higher correlation coefficients = increased ability
to predict one variable based on the other
 SAT/ACT scores moderately correlated with
first year college GPA
 2 variables may be highly correlated, but not
causally related
 Foot size and vocabulary positively correlated
 Do larger feet cause larger vocabularies?
 The third variable problem
Inferential Statistics:
Interpreting Data/Drawing Conclusions
 Hypothesis testing: do observed findings
support the hypotheses?
 Are findings real or due to chance?
 Statistical significance = when the probability
that the observed findings are due to chance
is very low
 Very low = less than 5 chances in 100/ .05
Evaluating Research:
Methodological Pitfalls
 Sampling bias
 Placebo effects
 Distortions in self-report data:
 Social desirability bias
 Response set
 Experimenter bias
 the double-blind solution
Ethics in Psychological Research:
Do the Ends Justify the Means?
 The question of deception
 The question of animal research
 Controversy among psychologists and the
 Ethical standards for research: the American
Psychological Association
 Ensures both human and animal subjects
are treated with dignity
Figure 2.17 Ethics in research
The Internet and Psychological Research
 Internet-mediated research refers to studies
in which data collection occurs over the web.
 Possible Advantages
 Samples that are much larger and much
more diverse than the samples typically
used in laboratory research
 Have the potential to yield more diverse
and representative samples
The Internet and Psychological Research
 Potential Disadvantages
 Sampling bias resulting from self-selection
may be a more troublesome issue in
Internet-mediated research
 Web users tend to be younger, brighter,
and more affluent than nonusers
 Data are collected under far less controlled
conditions than in traditional studies